Imaging device

ABSTRACT

An image pickup device which can obtain an image of wide range picked up by a plurality of cameras is provided by preventing occurrence of parallax.  
     The image pickup device is constructed such that an object of wide range is divided into a plurality of divided object portions to be separately picked up by a plurality of image pickup elements and images of divided object portions are processed into one combined video image by a processing element to which information on video images supplied from the respective image pickup elements is input; the image pickup element includes a lens  21  and an image pickup element  23  which detects rays of light passed through the lens  21,  and when principal rays positioned in a Gauss area are selected from among the principal rays passing through the center of an aperture stop  22  of the lens  21  in the image pickup element and a point where linear components of the selected principal rays in an object side space are extended to intersect an optical axis is defined as an NP point  26,  in respective image pickup elements a position of the NP point  26  is set behind the image pickup element  23  and respective NP points of the plurality of image pickup elements are made to congregate within a predetermined radius area in which one NP point  26  is centered.

TECHNICAL FIELD

[0001] The present invention relates to an image pickup device which canpick up an image of wide range such as of all sky (of all directions).

BACKGROUND ART

[0002] Conventionally, there have been developed various kinds ofcameras in which a number of video cameras are accommodated in a casingto pick up an image of all directions or of whole circumferencesimultaneously.

[0003] Specifically, for example, in order to obtain an image of widerange such as a panoramic view when a certain point in space is set as aviewpoint and an image of its circumference is picked up on thehorizontal plane, as shown in FIGS. 8 and 9, there are disposed fourvideo cameras 1, 2, 3, and 4 around a point I at equal intervals, inwhich each optical axis of lenses 5, 6, 7, and 8 of the respective videocameras 1, 2, 3, and 4 is fixed in emitting directions.

[0004] An image of 360° can be obtained by the above four cameras 1, 2,3, and 4 with a portion 10 of each image pickup area 9 being overlappedand then by putting together the overlapped portions.

[0005] However, in the above-described conventional image pickup device,each horizontal angle of view of video cameras 1, 2, 3, and 4 isrequired to be 90° or more, and as shown in FIG. 9, what is calledparallax occurs in the portion 10 where the two image pickup areas 9 ofvideo cameras 3, 4 overlap.

[0006] Since the value of parallax differs depending on the distancebetween a camera and an object, when the respective images taken by thecameras 3 and 4 are put together, the obtained image varies according tothe reference position determined within the overlapped portion 10.

[0007] Specifically, in order that images including parallax are puttogether for practical use, the reference position is required to bedetermined according to judgment in which an important part of the imageis visually judged by an editor. Accordingly, it has been difficult tocombine video images automatically, and which becomes an obstacle toautomatic processing of the picked-up image.

[0008] In order to solve the above-described problems, according to thepresent invention, there is provided an image pickup device in which animage of wide range picked-up by a plurality of cameras is obtained bypreventing occurrence of the parallax.

DISCLOSURE OF THE INVENTION

[0009] An image pickup device according to the present invention is theimage pickup device in which an object of wide range is divided into aplurality of divided object portions to be separately picked up by aplurality of image pickup means, and images of divided object portionsare processed into one combined video image by processing means to whichinformation on video images supplied from the respective image pickupmeans is input, wherein the image pickup means includes an image pickupelement which detects a lens and rays of light passed through the lens,and when principal rays positioned in a Gauss area are selected fromamong the principal rays passing through the center of an aperture stopof the lens in the image pickup means and a point where linearcomponents of the selected principal rays in an object side space areextended to intersect an optical axis is defined as an NP point, the NPpoint is set behind the image pickup element in respective image pickupmeans and respective NP points of the plurality of image pickup meansare made to congregate within a predetermined radius area with one NPpoint being centered.

[0010] According to the above-described construction of the image pickupdevice of the present invention, since the NP point is set behind theimage pickup element in the respective image pickup means, each opticalsystem of the image pickup means does not interfere with light passes ofother image pickup means. Further, since each NP point of the pluralityof image pickup means is made to congregate within a predeterminedradius area parallax between the respective image pickup means can beeliminated.

BRIEF DESCRIPTION OF DRAWINGS

[0011]FIG. 1 is a view for explaining a constitutional principle of animage pickup device according to the present invention;

[0012]FIG. 2 is a view for explaining the principle of the image pickupdevice according to the present invention;

[0013]FIG. 3 is a plan view showing an example in which an NP point isin a lens;

[0014]FIG. 4 is a schematic constitutional view showing an image pickupunit constituting the image pickup device according to an embodiment ofthe present invention;

[0015]FIG. 5 is a view showing an embodiment of an image pickup devicein which a plurality of image pickup units shown in FIG. 4 are disposed;

[0016]FIG. 6 is a schematic constitutional view showing an image pickupunit constituting an image pickup device according to another embodimentof the present invention;

[0017]FIG. 7 is a view showing an embodiment of an image pickup devicein which a plurality of image pickup units shown in FIG. 6 are disposed;

[0018]FIG. 8 is a schematic constitutional view showing a conventionalimage pickup device; and

[0019]FIG. 9 is a plan view of the image pickup device shown in FIG. 8.

BEST MODE FOR CARRYING OUT INVENTION

[0020] The present invention is an image pickup device in which anobject of wide range is divided into a plurality of divided objectportions to be separately picked up by a plurality of image pickup meansand images of the divided object portions are processed into onecombined video image by processing means to which information on thevideo images supplied from the respective image pickup means is input,wherein the image pickup means includes an image pickup element whichdetects a lens and rays of light passed through the lens, and whenprincipal rays positioned in a Gauss area are selected from among theprincipal rays passing through the center of an aperture stop of thelens in the image pickup means and a point where linear components ofthe selected principal rays in the object side space are extended tointersect an optical axis is defined as an NP point, the NP point is setbehind the image pickup element in respective image pickup means andrespective NP points of the plurality of image pickup means are made tocongregate within a predetermined radius area with one NP point beingcentered.

[0021] In the above-described image pickup device according to thepresent invention, a predetermined radius is set to approximately 20 μmwith one NP point being centered.

[0022] Further, in the above-described image pickup device according tothe present invention, in each image pickup means an optical systemhaving a lens and an image pickup element is disposed such that theoptical system is included in the space defined by the lines which passthrough the NP point and periphery of the lens in each direction.

[0023] First, the present invention will be generally described beforeexplaining the specific embodiments thereof.

[0024] With respect to the design of a lens such as used in videocameras and the like, a plurality of lenses are combined to reducechromatic aberration, curvature of field and aberration such as flare asmuch as possible. Basically, such lenses are composed of a thin convexlens 201 as shown in FIG. 1, and at the focal point of the convex lens201 there is provided a video image pickup device 202 of a solid-stateimage pickup element such as a CCD, MOS or the like, or a film (202) ofimage pickup element 202 when a silver salt camera is used.

[0025] Then, in the image pickup device having such fundamentalstructure an angle of view α is defined approximately by a diameter d1of the image pickup element 202 and a distance d4 between the convexlens 201 and the image pickup element 202 (focal length) when the amountof refraction of the convex lens 201 is disregarded, and the angle ofview α is expressed as tan (α/2)=(d1/2)/(d4).

[0026] Accordingly, in the case where an image of an object is picked upusing such a camera, if the image is picked up by the camera beingrotated on an NP point (non-parallax point) 203 as a central point,which is later described and positioned at the center within the convexlens 201, parallax will not occur between the plurality of obtainedimages.

[0027] Here, it is noted that an NP point was detected as a result of anumber of experiments in which, based on the fundamentals of opticalsystems, inventors of the present invention and others studied how toreduce the parallax occurred when a plurality of images are puttogether, and hereinafter the NP point will be explained, as shown inFIG. 2, when light reflected on the object focuses into an image on aimage pickup unit 301 through an equivalent convex lens 300.

[0028] That is, the equivalent convex lens 300 is composed of aplurality of lenses 302 to 308, and an aperture stop 309 is providedbetween the lenses 304 and 305.

[0029] In FIG. 2, numeral 321 indicates a lens body and numeral 322indicates a camera.

[0030] Then, among innumerable principal rays passing through the centerof the aperture stop 309, principal rays 311 passing through the areaclosest to an optical axis 310, that is, the Gauss area where theaberration is smallest are selected.

[0031] A point where linear components in the object side space 312 ofthe selected principal rays 311 are extended to intersect the opticalaxis 310 is set as an NP point (non-parallax point) 313.

[0032] Then, after the existence of the NP point 313 is verified, thepresent invention is further applied to a case where a plurality ofcameras are employed, that is, a plurality of cameras are simultaneouslyused to pick up an image instead of rotating one camera.

[0033] As shown in FIG. 1, when only one convex lens 201 is used, theposition of the NP point 203 is limited to a particular point and it isphysically impossible to dispose a plurality of cameras whose NP pointsare common to each other.

[0034] On the other hand, it is verified that when a plurality of lensessuch as the equivalent convex lens 300 in FIG. 2 are combined, the NPpoint 313 can be set at an arbitrary position approximately on theextended line of the optical axis 310.

[0035] When an image is picked up using a plurality of camerassimultaneously, in order to make respective NP points coincide there is,for example, such construction as positioning the NP point 313 in theair between the plurality of lenses (302 and 303) as shown in FIG. 2, oralthough not shown in the figure providing a mirror in front of a lensto pick up light reflected on the mirror by a camera and to make aposition of virtual image of the NP point of each camera coincide.

[0036] However, in either construction, an image pickup element andsignal processing circuit in a camera physically become obstacles toprevent picking up an image of all directions.

[0037] That is, when the NP point is within a lens as shown in FIG. 2,it is assumed that NP points 12 of respective cameras are made tocoincide at one point as shown in FIG. 3. FIG. 3 shows, for convenience,four angles of view 14, 15, 16, and 17 with respect to four cameras andboundaries 10 and 11 thereof.

[0038] In this case, one camera 13 (angle of view 14) which accommodatesan image pickup element and a signal processing circuit as shown in FIG.3 physically interferes with image pickup range of another camera (angleof view 16). Therefore, the interfered portion of the image cannot beobtained and accordingly the image of all directions cannot be obtained.

[0039] Although it is possible to lap a camera vertically over othercameras with the optical axes thereof being deviated from each other, anobtained image will be vertically misaligned in this case.

[0040] Therefore, according to the present invention, each NP point isdisposed behind the image pickup element in respective cameras, and allNP points of the cameras are made to be positioned within apredetermined radius area (spherical area) . Accordingly, parallax doesnot occur between images picked up by the cameras.

[0041] Then, in order to set the NP point behind the image pickupelement as described above, a plurality of lenses are to be combined toconstruct an optical system of a telephoto type.

[0042] In order to construct the optical system of a telephoto type andto set the NP point behind the image pickup element, for example, a lenshaving a function of a convex lens (function of convergence) is disposedon the object space side (object side), and a lens having a function ofa concave lens (function of divergence) is disposed on the image spaceside (image pickup element side).

[0043] Subsequently, an embodiment of the present invention will bedescribed.

[0044] In FIG. 4, a schematic constitutional view of an image pickupunit constituting the image pickup device is shown as an embodiment ofthe image pickup device according to the present invention.

[0045] The above image pickup unit comprises image pickup compound lensgroup 21 including a plurality of lenses, an aperture stop 22, an imagepickup element 23, and a signal processing unit 24, wherein the imagepickup compound lens group 21 and the aperture stop 22 are accommodatedin a lens body 25.

[0046] Then, in the image pickup compound lens group 21 a front compoundlens group 28 on the object space side (object side) has the function ofa convex lens (function of convergence) to constitute theabove-described telephoto type optical system.

[0047] According to the above construction, the NP point 26 can bepositioned behind the image pickup element 23.

[0048] Further, it is designed that the lens body 25 and the imageprocessing unit 24 are accommodated within the space defined by straightlines 27A and 27B which connect the periphery of a front lens 28 a andthe NP point 26, thereby enabling a video camera to be placed within thespace.

[0049] Accordingly, when a plurality of image pickup units shown in FIG.4 are disposed such that respective NP points 26 are made toapproximately coincide, the image pickup element 23 and the signalprocessing unit 24 become free from interfering with light paths ofother cameras, thereby enabling a video image of 360 degrees in alldirections including upper and lower, and right and left directions tobe picked up without parallax.

[0050] Specifically, making the NP points of respective image pickupunits approximately coincide is equivalent to setting the NP points ofrespective image pickup units within a predetermined radius area(spherical area).

[0051] In order to put together the images without parallax picked-up bythe respective image pickup units, the NP points of respective imagepickup units are constructed to be positioned at least within an area(sphere) of a radius of approximately 50 mm, preferably within an area(sphere) of a radius of approximately 20 mm (sphere).

[0052]FIG. 5 shows an embodiment of an image pickup device in which aplurality of image pickup units are disposed such that the position ofrespective NP points 26 of the image pickup units shown in FIG. 4approximately coincide.

[0053]FIG. 5 shows the image pickup device in which optical systems of atelephoto type including the front lens group 28 whose periphery ispentagonal are assembled into the shape of a regular dodecahedron.

[0054] This image pickup device is constructed such that among twelvefacets of the regular dodecahedron the bottom facet is used to attach asupport 43 or to lead out signal wires of respective cameras (not shownin the figure), and the other eleven facets each include one opticalsystem (refer to FIG. 4), that is, disposing eleven optical systems intotal.

[0055] It is obvious from this construction that disposing opticalsystems on a polyhedron enables a camera system which picks up an imageof approximately all the celestial sphere to be obtained.

[0056] With respect to the polyhedron, it is not limited to the regulardodecahedron shown in FIG. 5 and it may be a regular hexahedron (cube)or a regular icosahedron.

[0057] Further, although with respect to the polyhedron it is easy todesign a regular polyhedron, it is not necessary to be the regularpolyhedron depending on the design of an optical system.

[0058] According to the construction of the above-described embodiment,since a plurality of NP points 26 are made to coincide approximately,parallax of an image picked-up by each image pickup unit is eliminated.

[0059] Further, since the plurality of image pickup units are provided,it is possible to pick up an image of wide range such as an image ofapproximately all directions according to the construction shown in FIG.5.

[0060] Consequently, it becomes possible to pick up an image of alldirections without parallax.

[0061] Furthermore, since an image is picked up by a plurality of imagepickup units after dividing the image pickup range, picking-up an imageby each camera at high resolution enables the image of wide range to bepicked up at high resolution.

[0062] In FIG. 6, a schematic constitutional view of an image pickupunit constituting the image pickup device is shown as another embodimentof the image pickup device according to the present invention.

[0063] The above image pickup unit comprises a concave mirror 50, aconcave lens 51, an aperture stop 55, an image pickup element 52, and asignal processing unit 53.

[0064] Then, light from the outside is reflected on the concave mirror50 to enter the concave lens 51.

[0065] According to the construction of the above image pickup unit,since the light from the outside is reflected and converged by theconcave mirror 50, the concave mirror 50 has a function of a convex lens(function of convergence). Therefore, with the concave mirror 50 andanother optical-system including the concave lens 51 an optical systemof a telephoto type is constructed, and an NP point 56 is made to bepositioned behind the concave mirror 50.

[0066] In this construction, the space occupied by one image pickupdevice is the space defined by connecting the peripheries of the concavemirror 50 and the NP point 56, that is, within the straight lines 54 aand 54 b.

[0067] Then, when a plurality of image pickup units shown in FIG. 6 aredisposed such that the respective NP points 56 are made to approximatelycoincide, the image pickup element 52 and the signal processing unit 53become free from interfering with light paths of other cameras, therebyenabling a video image of 360 degrees in all directions including upperand lower, and right and left directions to be picked up withoutparallax.

[0068]FIG. 7 shows an embodiment of the image pickup device in which aplurality of image pickup units shown in FIG. 6 are disposed such thatthe respective NP points approximately coincide.

[0069]FIG. 7 shows the image pickup device in which optical systems of atelephoto type having a concave mirror 58 of an equilateral pentagon andrefractive optical-system 60 (lens) are assembled into the shape of aregular dodecahedron.

[0070] This image pickup device is constructed such that among twelvefacets of this regular dodecahedron the bottom facet is used to attach asupport 57 or to lead out signal wires of respective cameras (not shownin the figure), and the other eleven facets each include one opticalsystem (refer to FIG. 6), that is, disposing eleven optical system intotal. In FIG. 7, a numeral 59 represents stays which support therefractive optical-system 60 and a numeral 61 represents stays whichsupport the video cameras 62.

[0071] It is obvious from this construction that disposing opticalsystems on a polyhedron enables a camera system which picks up an imageof approximately all the celestial sphere to be obtained.

[0072] With respect to the polyhedron, it is not limited to the regulardodecahedron shown in FIG. 7, and it may be a regular hexahedron (cube)or a regular icosahedron.

[0073] Further, although with respect to a polyhedron it is easy todesign a regular polyhedron, it is not necessary to be the regularpolyhedron depending on the design of an optical system.

[0074] According to the above-described embodiment, similarly to theprevious embodiment, since a plurality of NP points 56 are made tocoincide approximately, parallax of an image picked-up by each imagepickup unit is eliminated and further it is possible to pick up an imageof wide range such as an image of all directions according to theconstruction shown in FIG. 7.

[0075] Consequently, it becomes possible to pick up an image of alldirections without parallax.

[0076] Furthermore, since an image is picked up by a plurality of imagepickup units after dividing the image pickup range, picking-up an imageby each camera at high resolution enables the image of wide range to bepicked up at high resolution.

[0077] Furthermore, in this embodiment, since the image pickup elements52 and the signal processing units 53 are disposed on the outside of thepolyhedron instead of being provided inside the polyhedron, constrainton dimensions of the polyhedron is mitigated, thereby enabling thepolyhedron to be smaller sized.

[0078] Although in the above-described embodiments the respective imagepickup units, whose NP points are made to approximately coincide,constitute a polyhedron to pick up an all-sky image, the presentinvention can be applied to other constructions.

[0079] For example, the present invention may be applied to aconstruction in which a part of, for example, the front half of allcelestial sphere is picked up by a plurality of image pickup units whoseNP points approximately coincide. Further, it may be possible to combineanother image pickup unit having a different NP point to pick up animage of other directions than those of the front half.

[0080] Further, for example, the present invention may be applied to aconstruction in which respective image pickup units are disposed on ahorizontal plane to pick up a strip-shaped image of 360 degrees inhorizontal direction.

[0081] The present invention is not limited to the embodiments describedabove, and can take various modifications without departing from thegist of the present invention.

[0082] According to the above-described embodiments, parallax betweenrespective image pickup units is eliminated and light paths of otherimage pickup units are not interfered.

[0083] Accordingly, an image of wide range, such as an image of alldirections can be picked up.

[0084] Further, since an image is picked up by a plurality of lenses andcameras after dividing the image pickup area, picking-up an image byeach camera at high resolution enables the image of wide range to bepicked up at high resolution.

1. An image pickup device in which an object of wide range is dividedinto a plurality of divided object portions to be separately picked upby a plurality of image pickup means and images of the divided objectportions are processed into one combined video image by processing meansto which information on video images supplied from said respective imagepickup means is input characterized in that: said image pickup meanscomprises a lens and an image pickup element which detects rays of lightpassed through said lens, and when from among principal rays passingthrough the center of an aperture stop of said lens in said image pickupmeans the principal rays positioned in Gauss area are selected and apoint where linear components of said selected principal rays in anobject side space are extended to intersect an optical axis is definedas an NP point, in said respective image pickup means, said NP point isset behind said image pickup element and respective NP points of saidplurality of image pickup means are made to congregate within apredetermined radius area in which one NP point is centered.
 2. An imagepickup device according to claim 1, wherein said predetermined radius isset to approximately 20 μm with one NP point being centered.
 3. An imagepickup device according to claim 1, wherein in said respective imagepickup means an optical system having said lens and said image pickupelement is disposed within a space defined by straight lines passingthrough said NP point and the periphery in each direction of said lens.